Aspirating two-way control valve



April 29, 1952 B. N. M DONALD 2,594,952

ASPIRATING TWO-WAY CONTROL VALVE Filed April 50, 1948 52 5764111 & WATERDRUM 56 PRIMARY SUPER/45A m2 A SP/RA T/NG' VAL V5 Fig. 2

INVENTOR' ATTORNEY Patented Apr. 29, 1952 UNITED STATES ram OFFICEBertrand N. McDonald, Aurora, 111., assignor to The Babcock & WilcoxCompany, New York, N. Y., a corporation of New Jersey Application April30, 1948, Serial No. 24,143

2 Claims. (Cl. 230-112) This invention relates to an aspiratmg two-waycontrol valve adapted for use in the superheated steam line of a steamgenerator.

The invention provides a unitary construction which constitutes anaspirator or ejector and steam flow proportioning valve, and a steammixer. It is particularly adapted to receive high pressure steam from aprimary superheater at one position, lower pressure steam from anattemperator at another position. The construction operates to controlthe division of steam flow through the high pressure and low pressureinlets; to adequately mix the attemperated steam and the by-passed steamon the downstream side of the attemperator; and to reduce the overallpressure drop because of the aspirating effect of the by-pass or highpressure steam.

The invention will be described by reference to the accompanyingdrawings which illustrate a preferred embodiment.

In the drawings:

Fig. l is a diagrammatic view illustrating a superheat control systemreceiving steam from a steam and water drum of a steam generator, andincluding a surface attemperator, in association with the unitarystructure which includes the steam proportioning valve and theaspirator; and

Fig. 2 is a detailed view of the unitary steam aspirator and valvestructure, in longitudinal section.

The unitary steam aspirator and steam proportioning valvev shown in thedrawings includes a tubular body l having a lateral inlet l2 for superheated steam, and a second lateral inlet 14 (usually of smaller flowarea) leading from a surface attemperator, the tubes of which may beadvantageously disposed in a submerged water drum 53 of the steamgenerator.

At spaced positions in tubular body ill and at opposite sides of theinlet [4, there are transverse metallic diaphragms and 22. Thesediaphragms are fixed within the tubular body in the positions shown andare formed with axially aligned openings which form bearings for thesliding movements of the hollow cylindrical member 24, the oppositesliding movements of which conversely vary the proportions ofsuperheated steam and attemperated, steam entering the valve body i0 andproceeding to a mixing zone 26 provided by a Venturi-like constructionhaving a contracting entrance portion 23 and an expanding exit portion30. The contracting entrance portion 23 of the Venturi insert member 30is formed as an extension of the conical converging wall 89 of the body10.

The hollow cylindrical valve member or valve plunger 24 is movedlongitudinally relative to the tubular body ID by means of a valve stem32 extending through a stuffing box construction 34 secured to a closuremember 36. which in turn is fixed to the left hand end of the body [0.The valve stem 32 has its right hand end secured to an end diaphragm orclosure member 3! secured to the member 24.

Fig. 2 shows the valve member or plunger 24 in an intermediate operatingposition slightly retracted from its fully advanced position indicatedby dot-dash lines A-A; the fully retracted position is indicated by thedot-dash indication B. In the position shown by Fig. 2, the annularsteam flow area of the opening 44 at position 46 in the conical portionof the body permits the flow of bypass steam, while steam flow from theattemperator through inlet into the central space of the plunger ispermitted through the ports 42 which are for the major portion of theirlength in the space 40 between diaphragms 20 and 22.

When the valve memberv 24 is retractively moved to the left from theposition in which it is shown in Fig. 2 (toward the position B) the flowof attemperated steam through the inlet l4 into the annular chamber 40and then into the valve member 24 is decreased by reason of thedecreased flow area of the communicating openings provided by thecircular series of parallel slots (or slot shaped ports) 42 formed inthe wall of the valve member 24 at its right hand end. This samemovement increases the flow area of the opening 44 between the righthand end of the valve member 24 and the conical wall portion 28 at theposition 46, toincrease the flow of superheated steam through the mixingzone 26.

The converging conical body portion 80 provides a rapidly increasingflow area 44 with progressive retractive movement so that a flow area ofminimum restriction leading from inlet l2 to the outlet end of the bodyis provided. When the plunger is so retracted the ports 42 will lie tothe left of diaphragm 20 and there will be no communicating fiowpassages into the central portion of the plunger from space 40.

With the longitudinally arranged ports 42 communicating fully withannular chamber 40. a free flow area of greater extent than that of theinlet I4 is conventiently provided to minimize the pressure droptherethrough. Static pressure conditions relative to the plunger aresuch at all positions that the force necessary to move it is small.making the valve readily adaptable for automatic regulation.

The retractive movement of the valve member 24 referred to above wouldbe accomplished when the temperature of the superheated steam at a pointof use beyond the zone 26 is such that a decreasing amount ofattemperation is necessary. Conversely an advancing movement of theplunger 24 toward the position AA would be accomplished when thesuperheat is higher than desired and it is desired to attemperate agreater proportion of the total steam flow.

The steam pressure and flow conditions under the arrangement indicatedin Fig. 2 of the drawings, as well as under the condition wherein thevalve member 24 is moved slightly to the left, include an aspiratingaction by the bypassed steam flowing from the inlet l2 through theopening 44 at the end of the valve member 24. The pressure of thesuperheated steam entering through the inlet 12 is greater than thepressure of the steam entering through the inlet M, and the velocityhead of the superheated steam flowing through the inlet I2 is increasedas the steam flows through the annular opening 44. This increase invelocity head is accompanied by a decrease in static pressure to therebycreate a pressure condition which provides for increased flow throughthe attemperator, the inlet M, the annular chamber 40, and the interiorof the valve member 24 to the position of the opening 44.

The steam flowing at high velocity through the annular opening 44 is,because of the conformation of the surrounding body wall and theentrance portion 28, directed inwardly in aspirating and mixingrelationship with the steam flowing axially from the open end of thevalve plunger 24. The gradually diverging portion of the Venturiconstruction contributes to the chicient recovery of velocity energy topressure energy as the velocity of the mixed stream is reduced.

From the above it will be appreciated that considerable advantageaccrues in the use of the described valve assembly in regulating theproportioning of the steam directed through an attemperator with respectto that directed about an attemperator in that the velocity conditionsresulting from the throttling of the bypassed steam are utilized inovercoming flow restrictive pressure loss conditions in the attemperatorflow path.

Fig. 1 of the drawings indicates the steam and water drum 50 of a steamgenerator. Such a generator may have steam heat absorbing steamgenerating tubes with their upper ends connected to the drum 50 andtheir lower ends connected to the submerged drum [8.

From the steam space of the drum 50, steam flow is to the superheaterinlet header 52, through circulators such as that shown at 54. From theheader 52, the steam flows through a bank 58 of series connected returnbend tubes which extend across a gas pass. From these tubes, the steamenters an intermediate superheater header 58 and then flows through atube such as that shown at 60 to a position 62 at which the steam flowis divided between the bypass 64 leading to the inlet [2, and theconduit 66 leading to the attemperator it, this .proportioning beingdependent upon the axial position of the valve member 24 within thevalve body in.

The flow of attemperated steam from the attemperator l6 to the inlet Mtakes place through the tubular connection 68. From the mixin zone 26 ofthe combined steam flow proportioning valve and steam aspirator, thesteam flow continues through the tubular connection 70 to a header (2for a secondary superheater 14 consisting of a bank of tubes similar tothe tubes of the bank 58 and similarly disposed transversel of the gaspass. From this bank of tubes steam flows through the superheater outletheader I6 and then through appropriate connections to a point of use.

The illustrative aspirating valve construction provides for the maximumof steam attemperation by movement of the hollow needle or valve member24 to the right from a position in which it is shown in Fig. 2. Whenthis movement is continued to the maximum extent, the beveled end 82 ofthe member 24 fits closely within the entrance of the contractingsection 28 of the mixing zone or within the tapered section 82 near theright hand end of the valve body [9, thus closing the bypass E54 andforcing all of the steam from the superneater 56 to flow through theattemperator l6.

While in accordance with the provisions of the statutes I haveillustrated and described herein the best form of my invention now knownto me, those skilled in the art will understand that changes may be madein the form of the apparatus disclosed without departing from the spiritof the invention covered by my claims, and that certain features of myinvention may sometimes be used to advantage without a corresponding useof other features.

What is claimed is:

1. In a combined mixing and aspirating valve construction, a tubularvalve body having a Venturi fluid mixing section and associated wallportions, a hollow tubular valve member closed at one end and having itsopen end arranged to contact the wall of the contracting entrance to theVenturi section when the valve member is moved in one of its directionsof movement, portions of the valve body having aligned openings andacting as slidable mounting means slidably receiving the valve memberand holding it in position coaxial with the Venturi, said last mentionedportions coacting with wall portions of the valve body to form twoseparated inlet chambers normally subjected to different fluidpressures, the inlet chamber nearest the Venturi being in directcommunication with the inlet of the Venturi when the valve member ismoved in one of its directions of movement, the interior of the valvemember being in free communication with the other inlet chamber throughopenings in a wall part of the valve member and the interior of thevalve member also being in free communication with the Venturi mixingsection, said last mentioned openings also extending longitudinally ofthe valve member so as to reduce the flow of fluid through the lastmentioned inlet chamber to the Venturi mixing section when the valvemember is moved to increase the flow from the remaining inlet chamber tothe Venturi, corresponding ends of adjacent longitudinally extendedopenings being adjacent said slidable mounting means when the valvemember is at one end of its path of movement and substantial parts ofthe openings being shrouded or rendered inoperative by the mountingmeanswhen the valve member has reached a position intermediate its path ofmovement, and means whereby the valve member may be moved longitudinallyof the valve body and toward or from the Venturi to reversely throttlethe flows from the two separate inlet chambers to the Venturi.

. 2. In a combined mixing and aspirating valve construction, a tubularbody having wall portions and a Venturi-like section at one end and twoaxially spaced separate fluid inlets at the same side of said section,said inlets being normally subject to difierent fluid pressures, atubular inner valve member, means within the valve body for slidablymounting the tubular inner valve member so that it is movable toward orfrom the contracting entrance of the Venturi section to control thefluid flow from said inlets to the Venturi section, said means combiningwith wall parts of the valve body to form separate inlet chambersseparately in communication with said inlets, the end of the valvemember remote from the venturi having longitudinally extending openingstherein in communication with the other of said inlet chambers andadapted to reduce the flow of fluid from the other inlet through theVenturi section as the valve is moved to increase the flow from thefirst inlet through the Venturi section, corresponding ends of adjacentlongitudinally extended openings being adjacent said slidable mountingmeans when the valve member is at one end of its path of movement andsubstantial parts of the openings being shrouded or renderedinoperativeby the mounting means when the valve member has reached a positionintermediate its path of movement, the interior of said valve membernormally in free communication with the Venturi section, and meanswhereby the valve member may be moved to reversely throttle the fluidflows from the separate inlets to the Venturi section solely by movementof the valve member in one direction.

BERTRAND N. MCDONALD.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number I Name Date 368,266 Wright Aug. 16, 18872,257,805 Kolling Oct. 7, 1941 2,364,211 Gustafson' Dec. 5, 1944 FOREIGNPATENTS Number Country Date 27,214 Switzerland Oct. 17, 1902

